The quality requirements of cold-rolled strip with respect to thickness tolerances, the attainability of certain final thicknesses, strip profiles or cross sections, strip planarities, etc. are continuously increasing in the course of developments. As a consequence of such developments, the requirements for flexible rolling mill concepts and modes of operation are likewise increasing and are required to be optimally matched to an end product to be rolled.
For the classical rolling mill types referred to as quarto or four-high mills and six-high or sexto mills there are aside from basic concepts with bending systems and fixed roll barrel shapes as roll gap influencing elements, two significant further rolling mill concepts which additionally affect the rolling gap by shifting of the working rolls or intermediate rolls based upon different effective principles. These are:
CVC/CVC-plus Technology and
The technology of strip-edge-oriented shifting of rolls.
Up to now both of these technologies have required different rolling mill concepts because different roll geometries were required for them.
In the classic CVC or continuous variable crown technology, the barrel-shaped lengths or contour lengths of the shiftable rolls was always longer than those of the fixed unshift-able rolls by the axial shifting stroke. The shiftable rolls thus need not have had their barrel terminating edge shifted beneath the stationary roll barrel. Thus surface damage or marking is avoided.
By contrast in the technology of strip-edge-oriented shifting, in the entire set of rolls, rolls with identical barrel or contour lengths are used. The shiftable rolls are thus shaped at the one side in the barrel edge region with a corresponding geometry, especially they can be provided with a taper. As a result, locally arising load peaks can be reduced.
The effective principle depends upon the strip-edge-oriented readjustment of the barrel edge, either ahead of, or at, or even behind the strip edge. Especially in the case of six-roll rolling mills, the shifting of the intermediate rolls beneath the backing roll gives rise to a targeted influence on the effectiveness of the positive work roll bending.